Photo-patternable dielectric materials and formulations and methods of use

ABSTRACT

Silsesquioxane polymers, silsesquioxane polymers in negative tone photo-patternable dielectric formulations, methods of forming structures using negative tone photo-patternable dielectric formulations containing silsesquioxane polymers, and structures made from silsesquioxane polymers.

RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.12/550,683 filed on Aug. 31, 2009.

FIELD OF THE INVENTION

The present invention relates to the field of photo-patternabledielectric materials; more specifically, it relates to patternabledielectric materials, photo-sensitive formulations containingpatternable dielectric materials, methods of using photo-sensitiveformulations containing patternable dielectric materials in thefabrication of integrated circuits, and integrated circuit structurescomprising patternable dielectric materials.

BACKGROUND OF THE INVENTION

Integrated circuits include, for example, active devices such as fieldeffect transistors partially formed in a semiconductor substrate andinterconnected by wiring levels comprising wires formed in interleveldielectric layers formed on the substrate. Conventional wiring levelsare formed by depositing an interlevel dielectric layer, patterning aphotoresist layer formed on the dielectric layer, etching trenches inthe dielectric layer, removing the photoresist and filling the trencheswith metal. This is an expensive and time-consuming process.Accordingly, there exists a need in the art to mitigate the deficienciesand limitations described hereinabove.

SUMMARY OF THE INVENTION

A first aspect of the present invention is a composition of mattercomprising: a silsesquioxane polymer comprising three or four monomersof the structural formulas (1), (2), (3), (4):

wherein two of the three or four monomers are structures (1) and (2);wherein R¹ is selected from the group consisting of linear alkyl,branched alkyl, cycloalkyl, aromatic, arene and ester moieties; whereinR² is selected from the group consisting of vinyl, substituted-vinyl,acetylenic, substituted acetylenic and nitrile moieties; wherein R³ isselected from the group consisting of linear alkyl, branched alkyl andcycloalkyl moieties; wherein R⁴ is selected from the group consisting oflinear alkoxy, branched alkoxy, cycloalkoxy, acetoxys, hydroxyl,silyloxy and silanol moieties; and wherein m, n, o, and p represent themole percent (mol %) of repeating units with m+n+o+p equal to or greaterthan about 40 mol % and wherein when only three monomers are presenteither o or p is zero.

A second aspect of the present invention is a photoactive formulation,comprising: a photoacid generator; a casting solvent; and asilsesquioxane polymer comprising three or four monomers of thestructural formulas (1), (2), (3), (4):

wherein two of the three or four monomers are structures (1) and (2);wherein R¹ is selected from the group consisting of linear alkyl,branched alkyl, cycloalkyl, aromatic, arene and ester moieties; whereinR² is selected from the group consisting of vinyl, substituted-vinyl,acetylenic, substituted acetylenic and nitrile moieties; wherein R³ isselected from the group consisting of linear alkyl, branched alkyl andcycloalkyl moieties; wherein R⁴ is selected from the group consisting oflinear alkoxy, branched alkoxy, cycloalkoxy, acetoxys, hydroxyl,silyloxy and silanol moieties; and wherein m, n, o, and p represent themole percent (mol %) of repeating units with m+n+o+p equal to or greaterthan about 40 mol % and wherein when only three monomers are presenteither o or p is zero.

A third aspect of the present invention is a method, comprising: (a)forming on a substrate, a layer of a photoactive formulation comprising:a photoacid generator; a casting solvent; and a silsesquioxane polymer;(b) patternwise exposing the layer with ultraviolet light to generate anexposed layer; (c) baking the exposed layer to cross-link thesilsesquioxane polymer in regions of the exposed layer exposed to theultraviolet light to generate a baked layer; (d) developing the bakedlayer to remove portions of the baked layer not exposed to theultraviolet light to form a first trench in a developed layer; (e)curing the developed layer to further cross-link the silsesquioxanepolymer and form a patterned cured layer including the first trench; and(f) filling the first trench in the patterned cured layer with anelectrically conductive material.

A fourth aspect of the present invention is a structure, comprising: across-linked layer of a silsesquioxane polymer or a silsesquioxanepolymer on a substrate; a trench in the cross-linked layer; anelectrically conductive material filling the trench and contacting thesubstrate in a bottom of the trench; and wherein the silsesquioxanepolymer comprises three or four monomers of the structural formulas (1),(2), (3), (4):

wherein two of the three or four monomers are structures (1) and (2);wherein R¹ is selected from the group consisting of linear alkyl,branched alkyl, cycloalkyl, aromatic, arene and ester moieties; whereinR² is selected from the group consisting of vinyl, substituted-vinyl,acetylenic, substituted acetylenic and nitrile moieties; wherein R³ isselected from the group consisting of linear alkyl, branched alkyl andcycloalkyl moieties; wherein R⁴ is selected from the group consisting oflinear alkoxy, branched alkoxy, cycloalkoxy, acetoxys, hydroxyl,silyloxy and silanol moieties; and wherein m, n, o, and p represent themole percent (mol %) of repeating units with m+n+o+p equal to or greaterthan about 40 mol % and wherein when only three monomers are presenteither o or p is zero.

These and other aspects of the invention are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention are set forth in the appended claims. Theinvention itself, however, will be best understood by reference to thefollowing detailed description of an illustrative embodiment when readin conjunction with the accompanying drawings, wherein:

FIGS. 1A through 1C illustrate steps in a method of forming single ordual-damascene wires using a photo-patternable dielectric materialaccording to embodiments of the present invention;

FIGS. 2A and 2B illustrate steps in a method of forming single damascenewires in a photo-patternable dielectric material according toembodiments of the present invention;

FIGS. 3A through 3E illustrate steps in a method of formingdual-damascene wires in a photo-patternable dielectric materialaccording to embodiments of the present invention;

FIG. 4 is a flowchart describing a method of forming single- and dualdamascene wires in dielectric material formed using a negative tonephoto-patternable dielectric formulation according to embodiments of thepresent invention;

FIG. 5 is a set of transmittance vs. wavenumber infrared spectra forsamples generated from a negative tone photo-patternable dielectricformulation according to embodiments of the present invention atdifferent processing steps; and

FIGS. 6 and 7 are scanning electron microscope photographs of dielectricstructures formed using a negative tone photo-patternable dielectricformulation according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention describes silsesquioxane polymers, which in afirst example are terpolymers and in a second example are silsesquioxanequadpolymers that may be mixed with one or more photoacid generators, anoptional casting solvent and one or more optional additives to form anegative tone photo-patternable dielectric formulation. Thesilsesquioxane polymers in the embodiments of the present invention maybe linear polymers, branched polymers, caged polymers or combinations ofthereof. The silsesquioxane polymers of embodiments of the presentinvention are preferably aqueous base soluble. Patternwise exposure of alayer of the formulation directly forms a cross-linked patterneddielectric layer (without the use of photoresist based lithography oretching of the dielectric layer) after development. After curing tofurther cross-link the patterned dielectric layer a low dielectricconstant (k) patterned dielectric layer is produced. A low-k material isdefined as a material having a dielectric constant of about 3.0 or less.The silsesquioxane polymers of the present invention may preferablycontain silanol endgroups with silyl ethers and silyl alcohols preferred(and may contain monomers having silanol moieties with silyl ethers andsilyl alcohols preferred) which cause cross-linking via condensationpolymerization in the presence of acid released by the photoacidgenerator after exposure to light (heat increases the efficiency of thepolymerization). Cross-linking enables the formation of chemical bonds,which can withstand standard thermal curing and subsequent curingconditions such as ultraviolet (UV)-thermal treatment. Thesilsesquioxane polymers of the present invention preferably contain atleast one monomer having a vinyl or an acetylenic moiety which furthercrosslinks the polymer during the curing process. The additionalcrosslinking provided by reacting the vinyl or acetylenic moietyimproves the mechanical properties of the material which is highlydesirable for creating robust low-k materials.

The silsesquioxane polymers of the present invention are particularlyuseful in forming damascene and dual-damascene wires without the use ofa photoresist since they can be patterned directly.

A damascene process is one in which a dielectric layer having wiretrenches or via openings extending through a dielectric layer is formed,an electrical conductor of sufficient thickness to fill the trenches isdeposited in the trenches and on a top surface of the dielectric, and achemical-mechanical-polish (CMP) process is performed to remove excessconductor and make the surface of the conductor co-planar with thesurface of the dielectric layer to form damascene wires (or damascenevias). When only a trench and a wire (or a via opening and a via) areformed the process is called single-damascene.

A via-first dual-damascene process (according to embodiments of thepresent invention) is one in which a first dielectric layer having viaopenings extending through the first dielectric layer are formedfollowed by formation of a second dielectric layer having trenchesextending through the second dielectric layer and intersecting thetrenches in the first dielectric layer. All via openings are intersectedby integral wire trenches above, but not all trenches need intersect avia opening. An electrical conductor of sufficient thickness to fill thetrenches and via openings is deposited on a top surface of thedielectric and a CMP process is performed to make the surface of theconductor in the trench co-planar with the surface the dielectric layerto form dual-damascene wires and dual-damascene wires having integraldual-damascene vias.

In silsesquioxane polymers according to embodiments of the presentinvention, R¹ is selected from the group consisting of linear alkyl,branched alkyl, cycloalkyl, aromatic, arene and ester moieties; R² is aselected from the group consisting of vinyl, substituted-vinyl,acetylenic, substituted acetylenic and nitrile moieties; R³ is selectedfrom the group consisting of linear alkyl, branched alkyl and cycloalkylmoieties; and R⁴ is selected from the group consisting of linear alkoxy,branched alkoxy, cycloalkoxy, acetoxys, hydroxyl, silyloxy and silanolmoieties. Preferred R¹ moieties are selected from the group consistingof methyl, ethyl, propyl, isopropyl, cyclohexyl, and norbornyl groups. Apreferred R² moiety is a vinyl group. A preferred R³ moiety is an ethylgroup. A preferred R⁴ moiety is a hydroxyl group.

In one example, the silsesquioxane polymers of the present inventioncomprise three or four monomers of the structural formulas (1), (2), (3)(4):

wherein R¹ is a carbon containing group for controlling polymerdissolution in aqueous base; R² is a vinyl or acetylenic moiety forcross-linking during post exposure baking (described infra); R³ is aC₁-C₁₈ hydrocarbon moiety and structural formula (3) is a bridge monomer(allows branched polymers); and R⁴ is a hydroxyl, alkoxy, silyloxy, or asilanol moiety for cross-linking during curing (described infra), and m,n, o, and p represent the mole percent (mol %) of repeating units. Mol %is mol-fraction times 100. mol % is thus 0.1 mol fraction. 10 mol %indicates that there is 1 mole of monomer in each 10 moles of polymer.The silsesquioxane polymers of the embodiments of the present inventionhave hydroxyl, alkoxy, silyloxy or silanol endgroups.

In one example, silsesquioxane polymers according to the presentinvention comprise monomers of structural formulas (1), (2) and (3) withm+n+o equal to or greater than about 40 mol %, with equal to or greaterthan about 75% preferred, equal to or greater than about 95% morepreferred, and equal to or greater than about 99% still more preferred.In one example, silsesquioxane polymers according to the presentinvention comprise monomers of structural formulas (1), (2) and (4) withm+n+p equal to or greater than about 40 mol %, with equal to or greaterthan about 75% preferred, equal to or greater than about 95% morepreferred, and equal to or greater than about 99% still more preferred.In one example polymers according to the present invention comprisemonomers of structural formulas (1), (2), (3) and (4) with m+n+o+p equalor greater than about 40 mol %, with equal to or greater than about 75%preferred, equal to or greater than about 95% more preferred, and equalto or greater than about 99% still more preferred.

In one example, for silsesquioxane polymers, m is between about 30 mol %and about 90 mol %, n is between 1 mol % and about 30 mol %, o isbetween about 0 mol % and about 10 mol % and p is between about 0 mol %and about 20 mol % of the final polymer composition, where 0 mol %indicates the monomer is not present in the polymer. When a monomer ofstructure (3) is present in the polymer, o has a minimum value of about0.5 mol %. When a monomer of structural formula (4) is present in thepolymer, p has a minimum value of about 0.5 mol %.

In one example, the silsesquioxane polymers of the present inventionconsist essentially of three or four monomers of the structural formulas(1), (2), (3) (4):

wherein R¹ is a carbon containing group for controlling polymerdissolution in aqueous base; R² is a vinyl or acetylenic moiety forcross-linking during post exposure baking (described infra); R³ is aC₁-C₁₈ hydrocarbon moiety and structural formula (3) is a bridge monomer(allows branched polymers); and R⁴ is a hydroxyl, alkoxy, silyloxy, or asilanol moiety for cross-linking during curing (described infra), andm+n+o+p is equal to about 100 mol %.

In a preferred first silsesquioxane terpolymer, consisting essentiallyof monomers of structural formulas (1), (2) and (3) of the invention, R¹is a methyl moiety and m is between about 70 mol % and about 80 mol %,R² is a vinyl moiety and n is between about 3 mol % and about 13 mol %,and R³ is an ethyl moiety and o is between about 0.5 mol % and about 6mol %.

In a preferred second silsesquioxane terpolymer, consisting essentiallyof monomers of structural formulas (1), (2) and (4) of the invention, R¹is a methyl moiety and m is between about 70 mol % and about 80 mol %,R² is a vinyl moiety and n is between about 3 mol % and about 13 mol %,and R⁴ is a hydroxyl moiety and p is between about 2 mol % and about 10mol %.

In a preferred silsesquioxane quadpolymer, consisting essentially ofmonomers of structural formulas (1), (2), (3) and (4), R¹ is a methylmoiety and m is between about 70 mol % and about 80 mol %, R² is a vinylmoiety and n is between about 3 mol % and about 13 mol %, R³ is an ethylmoiety and o is between about 0.5 mol % and about 6 mol %, and R⁴ is ahydroxyl moiety and p is between about 2 mol % and about 10 mol %.

In one example, the silsesquioxane polymers of the embodiments of thepresent invention have a weight-averaged molecular weight between about400 Daltons and about 500,000 Daltons. In one example, thesilsesquioxane polymers of the embodiments of the present invention havea weight-averaged molecular weight between about 1,500 Daltons and about20,000 Daltons.

Negative tone photo-patternable dielectric formulations according toembodiments of the of the present invention include the silsesquioxaneterpolymers and silsesquioxane quadpolymers of combinations of monomers(1), (2), (3) and (4) discussed supra, a photoacid generator (PAG), anda casting solvent. Negative tone photo-patternable dielectricformulations according to embodiments of the present invention mayoptionally include one or more additives such as organic bases,cross-linking agents and additive polymers.

Examples of PAGs include, but are not limited to, triphenylsulfoniumnonaflate,co(trifluoro-methylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide(MDT), N-hydroxy-naphthalimide (DDSN), onium salts, aromatic diazoniumsalts, sulfonium salts, diaryliodonium salts, and sulfonic acid estersof N-hydroxyamides, imides, or combinations thereof.

Examples of casting solvents include, but are limited to,ethoxyethylpropionate (EEP), a combination of EEP and γ-butyrolactone,propylene-glycol monomethylether acetate (PGMEA) propylene-glycolmonomethylether alcohol, propyleneglycol monopropyl alcohol,propyleneglycol monopropyl acetate, ethyl lactate, or combinationsthereof.

The organic base may be any suitable organic base known in thephotoresist art. Examples of organic bases include, but are not limitedto, tetraalkylammonium hydroxides, cetyltrimethylammonium hydroxide,1,8-diaminonaphthalene, and combinations thereof. The negative tonephoto-patternable dielectric formulations of the embodiments of thepresent invention are not limited to any specific selection of organicbase.

Examples of cross-linking agents include, but are not limited to,methylphenyltetramethoxymethyl glycouril (methylphenyl POWDERLINK),tetramethoxymethyl glycouril, methylpropyltetramethoxymethyl glycouril,and 2,6-bis(hydroxymethyl)-p-cresol.

An example of a polymer additive is the silsesquioxanes polymer havingthe structural formula:

wherein R⁵ is selected from the group consisting of alkyl, cycloalkyland aryl moieties and s is an integer between about 10 and about 1000.Many polymers of structural formula (5) are commercially available, forexample, from Dow Corning, Shin-Etsu, or JSR Corporation.

In one example, the silsesquioxane polymer additive possesses silanolend groups, but may also include halosilane, acetoxysilane, silylamine,and alkoxysilane endgroups. In a preferred embodiment of the presentinvention the additive polymer is a silsesquioxane polymer LKD-2015 (JSRCorporation) that contains silanol end groups.

The additive polymer comprises between about 1% by weight to about 99%by weight of all polymers of the negative tone photo-patternabledielectric formulations, with between about 20% by weight and 80% byweight preferred, and between about 30% by weight and 60% by weight morepreferred.

FIGS. 1A through 1C illustrate steps in a method of forming single ordual-damascene wires using a photo-patternable dielectric materialaccording to embodiments of the present invention. In FIG. 1A, aphoto-patternable dielectric layer 105 is formed on a substrate 100.Photo-patternable dielectric layer 105 is formed by spin coating,spraying or dip coating substrate 100 with a negative tonephoto-patternable dielectric formulation according to embodiments of thepresent invention described supra. If a negative tone photo-patternabledielectric formulation includes an optional casting solvent, afterapplying the negative tone photo-patternable dielectric formulation apre-exposure bake at a temperature between about 80° C. and about 120°C. with about 110° C. preferred is performed to drive out the castingsolvent and form photo-patternable dielectric layer 105. In one example,substrate 100 includes devices such as field effect transistors, bipolartransistors, diodes, resistors, capacitors and inductors as well ascontacts and damascene and/or dual-damascene wires (which wires may beformed using embodiments of the present invention or conventionalprocesses).

In FIG. 1B, photo-patternable dielectric layer 105 is patternwiseexposed to UV light through a mask 110. Mask 110 comprises a transparentor semi-transparent (to the wavelength of the UV light being used)substrate 115 having an opaque or semi-opaque to the wavelength of theUV light being used) image 120. More light passes through substrate 115than through the combination of substrate 115 and image 120. One image120 is illustrated, but there are typically hundreds of thousands tomillions of such images present on a mask used to form integratedcircuits. Upon exposure to the UV light, a pattern of unexposed regions125 and exposed regions 130 is formed in photo-patternable dielectriclayer 105. In one example, the UV light has a wavelength of about 248nm. In one example, the UV light has a wavelength of about 193 nm.

In FIG. 1C, a post exposure bake followed by a develop process followedby a curing process is performed to form a patterned dielectric layer135 having an opening 140 therein. A top surface 142 of substrate 140 isexposed in the bottom of opening 140. In one example, the post-exposurebake is performed at a temperature between about 35° C. and about 200°C. with a temperature between about 80° C. and about 120° C. preferred.The patternwise UV exposure causes the photoacid generator(s) inphoto-patternable dielectric layer 105 (see FIG. 1B) to generate acidwhich cross-links the polymer through the hydroxyl, alkoxy, silyloxy orsilanol endgroups and, if present, the R⁴ group of the structuralformula (4) monomers in regions 130 (see FIG. 1B) making the polymerinsoluble in basic developer. The post exposure bake enhances thiscross-linking process. Suitable developers include organic or aqueousbases with aqueous basic developers preferred. In one example thedeveloper is an aqueous solution of tetramethylammonium hydroxide. Inone example, the curing process is a bake at a temperature of about 400°C. or higher. In one example, the curing process is a UV exposure usinglight of a wavelength between about 50 nm and about 300 nm. In oneexample, the curing process includes simultaneous exposure to UV lightat a wavelength between about 50 nm and about 300 nm and heating toabout 400° C. or higher. The curing process cross-links the polymerthrough the R² group of the structural formula (2) monomers in regions130.

FIGS. 2A and 2B illustrate steps in a method of forming single damascenewires in a photo-patternable dielectric material according toembodiments of the present invention. FIG. 2A continues from FIG. 1C.

In FIG. 2A, a layer 145 of electrically conductive material is formed onthe top surface of patterned dielectric layer 135 and the top surface142 of substrate 100 exposed in opening 140. Layer 145 completely fillsopening 140. In one example, layer 145 comprises one or more layers ofmetal. In one example, layer 145 comprises a conformal layer of tantalumnitride in contact with patterned dielectric layer 135 (including thesidewalls of opening 140) and substrate 100, a conformal layer oftantalum on the tantalum nitride layer, and a copper layer (i.e., core)on the tantalum layer.

In FIG. 2B, planarization process (e.g., a chemical-mechanical-polish(CMP)) is performed so a top surface 147 of patterned dielectric layer135 is coplanar with a top surface 148 of single-damascene wire (orcontact) 150. Wire 150 may electrically contact a device (e.g., a gateelectrode of an FET) or another wire of a lower wiring level insubstrate 100.

FIGS. 3A through 3C illustrate steps in a method of formingdual-damascene wires in a photo-patternable dielectric materialaccording to embodiments of the present invention. FIG. 3A continuesfrom FIG. 1C.

In FIG. 3A, a photo-patternable dielectric layer 155 is formed on apatterned dielectric layer 135 filling opening 140. Photo-patternabledielectric layer 155 is formed by spin coating, spraying or dip coatingsubstrate 100 with a negative tone photo-patternable dielectricformulation according to embodiments of the present invention describedsupra. If a negative tone photo-patternable dielectric formulationincludes a optional casting solvent, after applying the negative tonephoto-patternable dielectric formulation a pre-exposure bake (e.g., at atemperature between about 80° C. and about 120° C. with about 110° C.preferred) is performed to drive out the casting solvent and formphoto-patternable dielectric layer 155.

In FIG. 3B, photo-patternable dielectric layer 155 is patternwiseexposed to ultraviolet (UV) light through a mask 160. Mask 160 comprisesa transparent or semi-transparent (to the wavelength of the UV lightbeing used) substrate 165 having an opaque or semi-opaque (to thewavelength of the UV light being used) image 160. More light passesthrough substrate 165 than through the combination of substrate 165 andimage 170. One image 160 is illustrated, but there are typicallyhundreds of thousands to millions of such images present on a mask usedto form integrated circuits. Upon exposure to the UV light, a pattern ofunexposed regions 175A and exposed regions 175B is formed inphoto-patternable dielectric layer 155. In one example, the UV light hasa wavelength of about 248 nm. In one example, the UV light has awavelength of about 193 nm.

In FIG. 3C, a post exposure bake followed by a develop process followedby a curing process is performed to form a patterned dielectric layer180 having an opening 185 therein. Opening 140 in patterned dielectriclayer 135 is exposed in the bottom of opening 185. Opening 140 has awidth W1 and opening 180 has a width W2 with W2>W1. In one example, thepost-exposure bake is performed at a temperature between about 35° C.and about 200° C., with a temperature between about 80° C. and about120° C. preferred. The patternwise UV exposure causes the photoacidgenerator(s) in photo-patternable dielectric layer 155 (see FIG. 3B) togenerate acid which cross-links the polymer through the hydroxyl,alkoxy, silyloxy or silanol endgroups and, if present, the R⁴ group ofstructural formula (4) monomers in regions 180 (see FIG. 3B) making thepolymer insoluble in basic developer. The post exposure bake enhancesthis cross-linking process. In one example, the curing process is a bakeat a temperature of about 400° C. or higher. In one example, the curingprocess is a UV exposure. In one example, the curing process includes acombination of exposure to UV light and heating to about 400° C. orhigher. In combination, the UV exposure and heating may be performedseparately or simultaneously. The curing process cross-links the polymerthrough the R² group of the structural formula (2) monomers in regions180.

In FIG. 3D, a layer 190 of electrically conductive material is formed onthe top surface of patterned dielectric layer 180, exposed surfaces ofpatterned dielectric layer 135, and the top surface 142 of substrate 100exposed in opening 140. Layer 190 completely fills openings 140 and 185.In one example, layer 190 comprises one or more layers of metal. In oneexample, layer 190 comprises a conformal layer of tantalum nitride incontact with patterned dielectric layers 135 and 180 (including thesidewalls of openings 140 and 180 and the top surface of patterneddielectric that was exposed in opening 185 in FIG. 3C) and substrate100, a conformal layer of tantalum on the tantalum nitride layer, and acopper layer (i.e., core) on the tantalum layer.

In FIG. 3E, a planarization process (e.g., a CMP) is performed so a topsurface 187 of patterned dielectric layer 180 is coplanar with a topsurface 188 of a dual-damascene wire 195. Wire 195 may electricallycontact another wire of a lower wiring level in substrate 100.

FIG. 4 is a flowchart describing a method of forming single- and dualdamascene wires in dielectric material formed using a negative tonephoto-patternable dielectric formulation according to embodiments of thepresent invention. In step 200, a negative tone photo-patternabledielectric formulation according to embodiments of the present inventionis applied to form a photo-patternable dielectric layer on a substrate(e.g., an integrated circuit undergoing fabrication) as illustrated inFIG. 1A and described supra. In step 205, the photo-patternabledielectric layer is patternwise exposed as illustrated in FIG. 1B anddescribed supra. In step 210, a post exposure bake is performed, in step215 the exposed photo-patternable dielectric layer is developed, and instep 220, the developed photo-patternable dielectric layer is cured toform a patterned dielectric layer as illustrated in FIG. 1C anddescribed supra.

In step 225, it is decided if the wire to be formed is to be asingle-damascene wire or a dual-damascene wire. If a single-damascenewire is to be formed the method proceeds to step 230.

In step 230, an electrically conductive layer as illustrated in FIG. 2Aand described supra is formed and in step 235 a planarization process asillustrated in FIG. 2B and described supra is performed to completefabrication of a single-damascene wire.

Returning to step 225, if a dual-damascene wire is to be formed themethod proceeds to step 240. In step 240, a negative tonephoto-patternable dielectric formulation according to embodiments of thepresent invention is applied to form a photo-patternable dielectriclayer on a substrate (e.g., an integrated circuit undergoingfabrication) as illustrated in FIG. 3A and described supra. In step 245,the photo-patternable dielectric layer is patternwise exposed asillustrated in FIG. 3B and described supra. In step 250, a post exposurebake is performed, in step 255 the exposed photo-patternable dielectriclayer is developed, and in step 260, the developed photo-patternabledielectric layer is cured to form a patterned dielectric layer asillustrated in FIG. 3C and described supra. In step 265, an electricallyconductive layer as illustrated in FIG. 3D and described supra is formedand in step 270 a planarization process as illustrated in FIG. 3E anddescribed supra is performed to complete fabrication of a dual-damascenewire.

FIG. 5 is a set of transmittance vs. wavenumber infrared spectra forsamples generated from a negative tone photo-patternable dielectricformulation according to embodiments of the present invention atdifferent processing steps. In FIG. 5, the upper spectrum (furthest fromthe wavenumber scale) is of a negative tone photo-patternable dielectricformulation as spun applied. The middle spectrum is after a thermal cureonly. The lower spectrum is after a combination UV and thermal cure. Thepeaks at about 1500 cm⁻¹ the pair of peaks around 3000 cm⁻¹ show the C═Cand ═C—H bands respectively of the R² group of the structural formula(2) monomer. The 1500 cm⁻¹ peak and the first peak of the pair at 3000cm⁻¹ diminish as cross-linking increases.

FIGS. 6 and 7 are scanning electron microscope photographs of dielectricstructures formed using a negative tone photo-patternable dielectricformulation according to embodiments of the present invention. Anegative tone photo-patternable dielectric formulation was prepared bymixing a 20 wt % solution ofpoly(methylsilsesquioxane-co-vinylsilsesquioxane-co-tetraethoxysilane)and 2 wt % of triphenylsulfonium nonaflate in PGMEA, and 0.4 wt % of anorganic base. The resulting low-k formulation was filtered through a 0.2μm filter. The low-k composition was spin coated onto an 8 inch siliconwafer and pre-exposure baked at 110° C. for 60 s, patternwise exposed to248 nm DUV light on an ASML (0.63 NA, ⅝ annular) DUV stepper, and postexposure baked at 110° C. for 60 seconds This was followed by a 30second puddle development step with aqueous 0.26 N tetramethyl ammoniumhydroxide (TMAH) developer to resolve 0.190 μm mask line and spacefeatures. FIG. 6 shows the structural formula of trenches generated withan 8 mJ exposure and FIG. 7 shows the structural formula of trenchesgenerated with an 11 mJ exposure.

EXAMPLES

The following examples provide further description of the presentinvention. The invention is not limited to the details of the examples.Where appropriate, the following techniques and equipment were utilizedin the Examples: ¹H and ¹³C NMR spectra were obtained at roomtemperature on an Avance 400 spectrometer. Quantitative ¹³C NMR was runat room temperature in acetone-d₆ in an inverse-gated ¹H-decoupled modeusing Cr(acac)₃ as a relaxation agent on an Avance 400 spectrometer.Thermo-gravimetric analysis (TGA) was performed at a heating rate of 5°C./min in N₂ on a TA Instrument Hi-Res TGA 2950 ThermogravimetricAnalyzer. Differential scanning calorimetry (DSC) was performed at aheating rate of 10° C./min on a TA Instruments DSC 2920 modulateddifferential scanning calorimeter. Molecular weights were measured intetrahydrofuran (THF) on a Waters Model 150 chromatograph relative topolystyrene standards. IR spectra were recorded on a Nicolet 510 FT-IRspectrometer on a film cast on a KBr plate. Film thickness was measuredon a Tencor alpha-step 2000. A quartz crystal microbalance (QCM) wasused to study the dissolution kinetics of the resist films in an aqueoustetramethylammonium hydroxide (TMAH) solution (CD-26).

When terpolymers and quadpolymers according to the present invention aresynthesized using triethoxymethylsilane, the monomer of structuralformula (1) is generated with R¹ being —CH₃ and the monomer may becalled methylsilsdesquioxane. When terpolymers and quadpolymersaccording to the present invention are synthesized usingtriethoxyvinylsilane, the monomer of structural formula (2) is generatedwith R² being —CH═CH₂ and the monomer may be called vinylsilsesquioxane.When terpolymers and quadpolymers according to the present invention aresynthesized using bis-trimethoxysilyl ethane, the monomer of structuralformula (3) is generated with R³ being —CH₂—CH₂— and the monomer may becalled bis-silsequioxylethane. When terpolymers and quadpolymersaccording to the present invention are synthesized usingtertaethoxysilane, the monomer of structural formula (4) is generatedwith R⁴ being O—CH₂—CH₃ and the monomer may be called tetraethoxysilane.

Example 1 Synthesis ofPoly[(methylsilsesquioxane-co-vinylsilsesquioxane-co-tetraethoxysilane)]

A 250 milliliter (ml) three neck round-bottom flask equipped with athermocouple thermometer, magnetic stirrer, condenser with nitrogeninlet, and a temperature controlled heating mantle was charged with amixture of triethoxymethylsilane (42.12 grams, 0.24 moles),triethoxyvinylsilane (6.25 g, 0.03 mole), tetraethoxysilane (5.71 grams,0.03 moles), 54.7 grams of methyl isobutyl ketone and 21 ml of a 1.75%solution of oxalic acid in water. The mixture was heated with stirringunder nitrogen. The reaction mixture was initially inhomogeneous, butafter 10 minutes at reflux became homogeneous with a reflux temperatureof 80° C. The reflux was continued for a total of 7 hours. The mixturewas cooled to room temperature and diluted with 50 ml of ethyl acetate.This mixture was extracted with six 50 ml portions of deionized water(final water extract was neutral to pH paper). The organic layer wasevaporated to yield 22.50 grams of a hard foam after evacuation at highvacuum and room temperature for 24 hours. Inverse gated ¹³C NMR inacetone in the presence of chromium acetylacetonate gave a ratio ofvinyl carbons to methyl carbons of 2:8.

Example 2 Synthesis ofPoly[(methylsilsesquioxane-co-vinylsilsesquioxane-co-bis-silsesquioxylethane-co-tetraethoxysilane)]

A 250 ml three neck round-bottom flask equipped with a thermocouplethermometer, magnetic stirrer, condenser with nitrogen inlet, and atemperature controlled heating mantle was charged with a mixture oftriethoxymethylsilane (49.92 grams, 0.28 moles), triethoxyvinylsilane(3.81 g, 0.02 mole), Tetraethoxysilane (8.33 grams, 0.04 moles),bis-trimethoxysilyl ethane (5.41 grams, 0.02 mole), 67.5 grams of methylisobutyl ketone and 25.2 ml of a 1.75% solution of oxalic acid in water.The mixture was heated with stirring under nitrogen. The reactionmixture was initially inhomogeneous, but after 10 minutes at refluxbecame homogeneous with a reflux temperature of 79.3° C. The reflux wascontinued for a total of 7 hours. The mixture was cooled to roomtemperature and diluted with 150 ml of ethyl acetate. This mixture wasextracted with two 150 ml portions of deionized water and filteredthrough a medium glass frit to remove traces of in-solubles. Thefiltered solution was washed with four additional 150 ml portions ofdeionized water (final water extract was neutral to pH paper). Theorganic layer was evaporated to yield 27.2 grams of a hard foam afterevacuation at high vacuum and room temperature for 24 hours. The molarratio of the monomers (1), (2), (3) and (4) was 14:1:1:2.

Example 3 Synthesis ofPoly[(methylsilsesquioxane-co-vinylsilsesquioxane-co-bis-silsesquioxylethane-co-tetraethoxysilane)]

A 250 ml three neck round-bottom flask equipped with a thermocouplethermometer, magnetic stirrer, condenser with nitrogen inlet, and atemperature controlled heating mantle was charged with a mixture oftriethoxymethylsilane (46.36 grams, 0.26 moles), triethoxyvinylsilane(7.61 g, 0.04 mole), Tetraethoxysilane (8.33 grams, 0.04 moles),bis-trimethoxysilyl ethane (5.41 grams, 0.02 mole), 67.5 grams of methylisobutyl ketone and 25.2 ml of a 1.75% solution of oxalic acid in water.The mixture was heated with stirring under nitrogen. The reactionmixture was initially inhomogeneous, but after 10 minutes at refluxbecame homogeneous with a reflux temperature of 79.4° C. The reflux wascontinued for a total of 7 hours. The mixture was cooled to roomtemperature and diluted with 150 ml of ethyl acetate. This mixture wasextracted with six 150 ml portions of deionized water (final waterextract was neutral to pH paper). The organic layer was evaporated toyield 30.07 grams of a hard foam after evacuation at high vacuum androom temperature for 24 hours. The molar ratio of the monomers (1), (2),(3) and (4) was 13:2:2:1.

Example 4 Synthesis ofPoly[(methylsilsesquioxane-co-vinylsilsesquioxane-co-bis-silsesquioxylethane)]

Methyltriethoxysilane (53.49 grams, 0.3 mole), vinyltriethoxysilane(20.76 grams, 0.109 mole), bis(triethoxysilane)ethane (7.38 grams, 0.026mole), and tetra orthosilicate (11.36 grams, 0.055 mole) were mixedtogether with 4-methyl-2-pentanone (77.78 ml) in a three-necked 500milliliter round-bottom flask. 1.75 wt % oxalic acid solution (25.2grams) was added to the above solution at 60° C. resulting in anexothermic reaction. The temperature of the reaction mixture was broughtdown to 70° C., and thereafter the reaction mixture was stirred at 78.8°C. for 6 hours. To extract the polymer, ethyl acetate (150 ml) was addedto the reaction mixture at room temperature and the solution was washed(7-8 times) with distilled water. Evaporating the solvent under reducedpressure afforded the polymer (27 gram).

Example 5 Nanoindentation Measurements

The Young's modulus for the cured materials was determined bynanoindentation. Films of a controlpoly(methylsilsesquoxane-co-bis-silsesquioxylethane) and twopoly(methylsilsesquioxane-co-vinylsilsesquioxane-co-bis-silsesquioxylethane-co-tetraethoxysilane)were spin applied onto a silicon wafers and then post-applied baked at110° C. for 1 min, exposed to 248 nm light, post-exposure baked at 110°C. for 1 min, and then UV-thermally cured at 400° C. The moleproportions of monomers of thepoly(methylsilsesquoxane-co-bis-silsesquioxylethane) was 15:1 and themeasured modulus was 5.4 GPa. The mole proportions of monomers of thefirstpoly(methylsilsesquioxane-co-vinylsilsesquioxane-co-bis-silsesquioxylethane-co-tetraethoxysilane)was 13.5:1.5:1 and the measured modulus was 9.9 GPa. The mole ratios ofmonomers of the second poly(methylsilsesquioxane-co-vinylsilsesquioxane-co-bis-silsesquioxylethane-co-tetraethoxysilane)was 13:2:1 and the measured modulus was 10.89 GPa

Example 6 Photo-Patterning

A patternable low-k composition was formulated with 20 wt % solution ofMethylsilsesquioxane-co-Vinylsilsesquioxane-co-TEOS and 2 wt % oftriphenylsulfonium nonaflate in PGMEA, and 0.4 parts of an organic base.The resulting low-k formulation was filtered through a 0.2 μm filter.The low-k composition was spin coated onto an 8 inch silicon wafer andpre-exposure baked at 110° C. for 60 seconds, patternwise exposed to 248nm DUV light on an ASML (0.63 NA, ⅝ annular) DUV stepper, and postexposure baked at 110° C. for 60 seconds. This was followed by a 30seconds puddle development step with 0.26 N TMAH developer to resolve0.190 μm line and space features.

Thus the embodiments of the present invention provides patternabledielectric materials, photo-sensitive formulations containingpatternable dielectric materials, methods of using photo-sensitiveformulations containing patternable dielectric materials in thefabrication of integrated circuits, and integrated circuit structurescomprising patternable dielectric materials. The methods according toembodiments of the present invention use less materials and require lesssteps than conventional methods.

The description of the embodiments of the present invention is givenabove for the understanding of the present invention. It will beunderstood that the invention is not limited to the particularembodiments described herein, but is capable of various modifications,rearrangements and substitutions as will now become apparent to thoseskilled in the art without departing from the scope of the invention.Therefore, it is intended that the following claims cover all suchmodifications and changes as fall within the true spirit and scope ofthe invention.

What is claimed is:
 1. A method, comprising; (a) forming on a substrate,a layer of a photoactive formulation comprising: a photoacid generator;a casting solvent; and a silsesquioxane polymer; (b) patternwiseexposing said layer with ultraviolet light to generate an exposed layer;(c) baking said exposed layer to cross-link said silsesquioxane polymerin regions of said exposed layer exposed to said ultraviolet light togenerate a baked layer; (d) developing said baked layer to removeportions of said baked layer not exposed to said ultraviolet light toform a first trench in a developed layer; (e) curing said developedlayer to further cross-link said silsesquioxane polymer and form apatterned cured layer including said first trench; and (f) filling saidfirst trench in said patterned cured layer with an electricallyconductive material.
 2. The method of claim 1, further including:between (e) and (f): forming an additional layer of a photoactiveformulation on said patterned cured layer, said addition cured layercomprising: a photoacid generator; a casting solvent; and asilsesquioxane terpolymer or a silsesquioxane quadpolymer; patternwiseexposing said additional layer with ultraviolet light to generate anadditional exposed layer; baking said additional exposed layer tocross-link said silsesquioxane terpolymer or said silsesquioxanequadpolymer in regions of said additional exposed layer exposed toultraviolet light to generate an additional baked layer; developing saidadditional baked layer to remove portions of said additional baked layernot exposed to ultraviolet light to form a second trench in anadditional developed layer; curing said additional developed layer tocross-link said silsesquioxane terpolymer or said silsesquioxanequadpolymer to form a patterned additional cured layer including saidsecond trench, said first trench exposed in a bottom of said secondtrench, said substrate exposed in said bottom of said first trench; andwherein (f) includes simultaneously filling said first trench and saidsecond trench with said electrically conductive material.
 3. The methodof claim 2, wherein said additional silsesquioxane polymer comprisesthree or four monomers of the structural formulas (1), (2), (3), (4):

wherein two of said three or four monomers are structures (1) and (2);wherein R¹ is selected from the group consisting of linear alkyl,branched alkyl, cycloalkyl, aromatic, arene and ester moieties; whereinR² is selected from the group consisting of vinyl, substituted-vinyl,acetylenic, substituted acetylenic and nitrile moieties; wherein R³ isselected from the group consisting of linear alkyl, branched alkyl andcycloalkyl moieties; wherein R⁴ is selected from the group consisting oflinear alkoxy, branched alkoxy, cycloalkoxy, acetoxys, hydroxyl,silyloxy and silanol moieties; and wherein m, n, o, and p represent themole percent (mol %) of repeating units with m+n+o+p equal to or greaterthan about 40 mol % and wherein when only three monomers are presenteither o or p is zero.
 4. The method of claim 1, wherein saidsilsesquioxane polymer comprises three or four monomers of thestructural formulas (1), (2), (3), (4):

wherein two of said three or four monomers are structures (1) and (2);wherein R¹ is selected from the group consisting of linear alkyl,branched alkyl, cycloalkyl, aromatic, arene and ester moieties; whereinR² is selected from the group consisting of vinyl, substituted-vinyl,acetylenic, substituted acetylenic and nitrile moieties; wherein R³ isselected from the group consisting of linear alkyl, branched alkyl andcycloalkyl moieties; wherein R⁴ is selected from the group consisting oflinear alkoxy, branched alkoxy, cycloalkoxy, acetoxys, hydroxyl,silyloxy and silanol moieties; and wherein m, n, o, and p represent themole percent (mol %) of repeating units with m+n+o+p equal to or greaterthan about 40 mol % and wherein when only three monomers are presenteither o or p is zero.
 5. The method of claim 1, wherein said curingcomprises simultaneous exposure to ultraviolet light and heating to atemperature of at least 400° C.
 6. The method of claim 1, wherein saidsilsesquioxane polymer consists essentially of monomers of structuralformulas (1), (2) and (3), R¹ is a methyl moiety and m is between about70 mol % and about 80 mol %, R² is a vinyl moiety and n is between about3 mol % and about 13 mol %, and R³ is an ethyl moiety and o is betweenabout 0.5 mol % and about 6 mol %.
 7. The method of claim 1, whereinsaid silsesquioxane polymer consists essentially of monomers ofstructural formulas (1), (2) and (4), R¹ is a methyl moiety and m isbetween about 70 mol % and about 80 mol %, R² is a vinyl moiety and n isbetween about 3 mol % and about 13 mol %, and R⁴ is a hydroxyl moietyand p is between about 2 mol % and about 10 mol %.
 8. The method ofclaim 1, wherein said silsesquioxane polymer consists essentially ofmonomers of structural formulas (1), (2), (3) and (4), R¹ is a methylmoiety and m is between about 70 mol % and about 80 mol %, R² is a vinylmoiety and n is between about 3 mol % and about 13 mol %, R³ is anethylene moiety and o is between about 0.5 mol % and about 6 mol %, andR⁴ is a hydroxyl moiety and p is between about 2 mol % and about 10 mol%.
 9. The method of claim 1 wherein said photoactive formulation furtherincludes: an additive silsesquioxane polymer of structure (5):

wherein R⁵ is selected from the group consisting of alkyl, cycloalkyland aryl moieties; and wherein s is an integer between about 10 andabout
 1000. 10. The method of claim 1, wherein photoactive formulationfurther includes: one or more cross-linking agents, one or more organicbases or combinations thereof.
 11. The method of claim 1, wherein saidsilsesquioxane polymer comprises four monomers of the structuralformulas (1), (2), (3), (4).
 12. A structure, comprising: a cross-linkedlayer of a silsesquioxane polymer or a silsesquioxane polymer on asubstrate; a trench in said cross-linked layer; an electricallyconductive material filling said trench and contacting said substrate ina bottom of said trench; and wherein said silsesquioxane polymercomprises three or four monomers of the structural formulas (1), (2),(3), (4):

wherein two of said three or four monomers are structures (1) and (2);wherein R¹ is selected from the group consisting of linear alkyl,branched alkyl, cycloalkyl, aromatic, arene and ester moieties; whereinR² is selected from the group consisting of vinyl, substituted-vinyl,acetylenic, substituted acetylenic and nitrile moieties; wherein R³ isselected from the group consisting of linear alkyl, branched alkyl andcycloalkyl moieties; wherein R⁴ is selected from the group consisting oflinear alkoxy, branched alkoxy, cycloalkoxy, acetoxys, hydroxyl,silyloxy and silanol moieties; and wherein m, n, o, and p represent themole percent (mol %) of repeating units with m+n+o+p equal to or greaterthan about 40 mol % and wherein when only three monomers are presenteither o or p is zero.
 13. The structure of claim 12, further including:an additional cross-linked layer of an additional silsesquioxane on saidcross-linked layer; an additional trench in said additional cross-linkedlayer, a top of said trench open to a bottom of said additional trench;and said electrically conductive material additionally filling saidadditional trench.
 14. The structure of claim 13, wherein saidadditional silsesquioxane polymer comprises three or four monomers ofthe structural formulas (1), (2), (3), (4):

wherein two of said three or four monomers are structures (1) and (2);wherein R¹ is selected from the group consisting of linear alkyl,branched alkyl, cycloalkyl, aromatic, arene and ester moieties; whereinR² is selected from the group consisting of vinyl, substituted-vinyl,acetylenic, substituted acetylenic and nitrile moieties; wherein R³ isselected from the group consisting of linear alkyl, branched alkyl andcycloalkyl moieties; wherein R⁴ is selected from the group consisting oflinear alkoxy, branched alkoxy, cycloalkoxy, acetoxys, hydroxyl,silyloxy and silanol moieties; and wherein m, n, o, and p represent themole percent (mol %) of repeating units with m+n+o+p equal to or greaterthan about 40 mol % and wherein when only three monomers are presenteither o or p is zero.
 15. The structure of claim 12, wherein saidcross-linked layer has a dielectric constant of about 3.0 or less. 16.The structure of claim 12, wherein said silsesquioxane polymer consistsessentially of monomers of structural formulas (1), (2) and (3), R¹ is amethyl moiety and m is between about 70 mol % and about 80 mol %, R² isa vinyl moiety and n is between about 3 mol % and about 13 mol %, and R³is an ethyl moiety and o is between about 0.5 mol % and about 6 mol %.17. The structure of claim 12, wherein said silsesquioxane polymerconsists essentially of monomers of structural formulas (1), (2) and(4), R¹ is a methyl moiety and m is between about 70 mol % and about 80mol %, R² is a vinyl moiety and n is between about 3 mol % and about 13mol %, and R⁴ is a hydroxyl moiety and p is between about 2 mol % andabout 10 mol %.
 18. The structure of claim 12, wherein saidsilsesquioxane polymer consists essentially of monomers of structuralformulas (1), (2), (3) and (4), R¹ is a methyl moiety and m is betweenabout 70 mol % and about 80 mol %, R² is a vinyl moiety and n is betweenabout 3 mol % and about 13 mol %, R³ is an ethylene moiety and o isbetween about 0.5 mol % and about 6 mol %, and R⁴ is a hydroxyl moietyand p is between about 2 mol % and about 10 mol %.
 19. The structure ofclaim 12, wherein said cross-linked layer further includes: an additivesilsesquioxane polymer of structure (5):

wherein R⁵ is selected from the group consisting of alkyl, cycloalkyland aryl moieties; and wherein s is an integer between about 10 andabout
 1000. 20. The structure of claim 12, wherein said silsesquioxanepolymer comprises four monomers of the structural formulas (1), (2),(3), (4).